I've written algorithms for machine learning, where I'm constantly doing things like multiplying 0 and infinity. And, depending on the situation it is totally clear what the correct result must be (either 0 or infinity).

But that is the key point - you're right that, in many situations, it makes sense to assign a particular value to 0/0 (and other pathological cases) - but the thing is that the value that needs to be chosen depends critically on the situation at hand. Sometimes 0/0 might need to be treated as 0, sometimes 1, sometimes 42, and sometimes it is indicative of an error. Only the person writing the program can know which value is appropriate for the circumstance, so they must express it explicitly in the program. If programming environments throw an exception in the case of 0/0, it indicates that the programmer has not considered this choice, and that there is therefore a bug; by contrast, choosing one particular value would make some small subset of implementations work, at the expense of making all the others (which needed different values, or an error) give the wrong answer without any indication of a problem.

How does any of this address parent's question ? How can he "do something as simple as changing my DNS servers" ?

The same way as before systemd came on the scene (unless your distro has changed things at the same time - and network settings are something distros do seem to like to move around from release to release - but systemd doesn't, as far as I'm aware, touch the DNS settings at all!)

but for example the american A in words like "cat" and "path" is historic, unlike the British pronunciations which match the a in "father"

You make some interesting points, but you clearly have some very strange ideas about British pronunciation:) For example, the vowel in "cat" (in "standard" British English - what, for example, most announcers would use on the BBC) is nothing like the vowel in "father". And many British accents are rhotic, too!

"So being lazy and using improper English is impolite to the extreme."

Motes and beams, people!
If you're going to moan about "improper" English, it's best not to make lots of errors yourself:
- you started your sentence with "So". The word you ought to have used was "Thus".
- you missed out the comma that should have followed the "So"
- the expression is "in the extreme", not "to the extreme"
- even had you used "in the extreme", it would still have made for an awkward and inelegant sentence, compared to the obvious alternate of "... is extremely impolite."

Do you have a credible source for any of these so-called rules? In particular:

This because it is Linux or the GNU toolchains that has issues with multiple lib versions (the major source of "dependency hell"), it is the package managers.

Actually the package managers can handle it just fine (well, I know RPM can, and I *think* dpkg/apt can too); usually the problem is that the libraries are packaged in a way that doesn't support this. If two versions of a package share no files (e.g. if you provide "libxyz.so.1.0.0" in one package, and "libxyz.so.1.1.0" in another version of the same package, RPM can handle having both versions of the package installed with no problems at all. This is used, for example, to support having multiple kernel versions installed on RedHat-type systems. What becomes a problem is if you have (say) binaries in the same package, with the same name in each version, but different contents: naturally RPM will report a conflict if you try to install both.

What would you propose as a better alternative to this idiom in a language that lacks exceptions:

I propose this; namely using variables to keep track of the state of resources, and then cleaning up based on the values of those variables. In my experience this is much less error-prone than the "goto" equivalent - for example, reordering the code is much less likely to break the cleanup.

You need to be an administrator to do that. That makes it pretty non-trivial.

It would, except that users having Admin access is much more common on Windows systems. (Being an Administrator on Windows does not (in theory, at least) have the complete "game over" privileges that "root" traditionally does on Unix-based systems, so there are still further privilege levels to be escalated to.)

is running a different OS which doesn't treat Ctrl+Alt+Del in a special way

Now your suggesting what exactly? That the attacker is going to throw in a linux live CD, boot it, run his 'fake login screen' that looks like the usual windows screen?

Ok... yes I guess that is a theoretically possible attack; although you'd probably get caught as soon as the user isn't actually able to log-in and IT gets called in...

Why would IT get called in? After the user's entered their password, you just display a simulated BSOD and then reboot into the genuine OS; no user will be remotely suprised;-)

I can trivially run a program to throw up a screen that looks like the login screen on a PC at work. TRIVIALLY.

Adding a registry entry to remap keys is pretty trivial, too... as, for that matter, is running a different OS which doesn't treat Ctrl+Alt+Del in a special way! Thus any extra security provided is minimal. Which is fine - as you say, security doesn't have to be perfect in order to be useful - but in my view overselling the effectiveness of a measure is counterproductive.

Nobody here is arguing ctrl-alt-delete is some magical super thing,

Alas that is exactly what Microsoft claimed for years (possibly still claim?)...